1. Technical Field
The present invention relates to a liquid crystal device in which liquid crystal is held between a pair of substrates and a projection type display apparatus which utilizes the liquid crystal device as a light valve.
2. Related Art
In a liquid crystal device, a first substrate, at which a pixel region which is configured by arranging a plurality of pixel electrodes at one face side is provided, and a second substrate, at which a common electrode to which a common potential is applied is provided, are bonded to each other by a seal material and a liquid crystal layer is held in a region surrounded by the seal material between the first substrate and the second substrate. Such a liquid crystal device is used as a light valve of a direct-view type display apparatus or a projection type display apparatus.
In such a liquid crystal device, if ionic impurities mixed in at the time of liquid crystal injection or ionic impurities eluted from the seal material aggregate within the pixel region by driving of the liquid crystal device, deterioration of display quality such as burning (staining) or the like of an image is caused. Therefore, there is proposed a technique of providing a peripheral electrode at the outside of the pixel region and preventing aggregation of the ionic impurities in the pixel region by such a peripheral electrode (refer to Paragraph [0049] or the like of JP-A-2006-171033, FIG. 4 or the like of JP-A-2008-58497, and Paragraph [0053] or the like of JP-A-2008-268253).
For example, in the technique described in JP-A-2006-171033, a peripheral electrode (dummy wiring electrode), to which the same electric potential as that of a common electrode is applied, is provided at a corner portion of a peripheral region and ionic impurities are drawn to the peripheral electrode. In the technique described in JP-A-2008-58497, a first peripheral electrode and a second peripheral electrode are provided so as to surround a pixel region and by applying different electric potentials to the first peripheral electrode and the second peripheral electrode and also inverting the polarity of the electric potentials which are applied to the first peripheral electrode and the second peripheral electrode for each frame, minute fluctuation of the liquid crystal and movement of ionic impurities are performed by a transverse electric field between the first peripheral electrode and the second peripheral electrode. In the technique described in JP-A-2008-268253, a peripheral electrode is provided so as to surround a pixel region and an electric potential having higher frequency than a signal which is applied to a pixel electrode is applied to the peripheral electrode, thereby moving ionic impurities to a peripheral region.
However, even in the technique described in any of JP-A-2006-171033, JP-A-2008-58497, and JP-A-2008-268253, there is a problem in that it is not possible to prevent deterioration of display quality due to ionic impurities. That is, as in the technique described in JP-A-2006-171033, in a case where the same electric potential is applied to the dummy wiring electrode of the first substrate side and the common electrode of the second substrate side, since an electric field cannot be formed between the dummy wiring electrode and the common electrode, there is a problem in that it is not possible to sufficiently draw in the ionic impurities. Also, as in the technique described in JP-A-2008-58497 and JP-A-2008-268253, in a case where the polarity of the electric potential which is applied to the peripheral electrode changes, for example, anionic impurities among the ionic impurities move toward the peripheral electrode when the electric potential of the peripheral electrode has a positive polarity. However, if the electric potential of the peripheral electrode is changed to a negative polarity, since the impurities move in a direction away from the peripheral electrode, there is a problem in that it is not possible to draw in and retain the ionic impurities in the vicinity of the peripheral electrode. Therefore, even in the technique described in any of JP-A-2006-171033, JP-A-2008-58497, and JP-A-2008-268253, since it is difficult to reliably prevent aggregation of the ionic impurities in the pixel region, there is a problem in that it is not possible to prevent deterioration of display quality due to ionic impurities.